Crown-ether containing copolymers as selective membranes for quartz crystal microbalance chemical sensors

Novel chemical sensors have been developed based on piezoelectric quartz resonators coated with chemically engineered copolymer resins. These have been employed for the selective detection in aqueous solution of K+ over other Group I ions such as Li+ and Na+. A quartz crystal microbalance, QCM, operating with 10 MHz, AT‐cut piezoelectric crystals and Au electrodes, forms the basis of the sensor set‐up where the frequency changes indicate a change in absorbed mass of the species of interest. The copolymer coating was designed to chelate specific ions from solution introducing selectivity to the sensor response. Acrylic acid polymers crosslinked with ethylene glycol dimethacrylate (EGDMA) and substituted with 18‐crown‐6 and the 15‐crown‐5 rings were synthesized and coated onto the crystal. The sensor was employed in a flow injection analysis (FIA) set‐up. The detection limit of the developed sensor is estimated at 0.4 ppm for $\hbox{\bf K}^{+}_{(\bf aq)}$, although further optimization should significantly reduce this value. © 2000 Society of Chemical Industry.